Rotator member to be fixed to rotary shaft of rotary electric machine, rotator including rotator member, and method for manufacturing rotary electric machine and rotator

ABSTRACT

A rotator member  300  includes a tubular sleeve  301  having a first end surface and a second end surface, a plurality of magnet segments  311  circumferentially disposed at a radially outside of the sleeve  301 , and a tubular member  321  adapted to cover the magnet segments  311  from a radially outside to hold the magnet segments  311  between the tubular member  321  and the sleeve  301 . The sleeve  301  has an inner circumference surface that includes a tapered surface that gradually and outside the radial direction expands in a direction from the first end surface toward the second end surface.

BACKGROUND ART

1. Technical Field

The present invention relates to a rotator member fixed to a rotaryshaft of a rotary electric machine, a rotator including the rotatormember, and a method for manufacturing the rotary electric machine andthe rotator.

2. Description of Related Art

When an electric motor using permanent magnets as a rotator is rotatedat a high speed, the electric motor has to be reinforced in order toendure centrifugal force generated during high speed rotation withrespect to strength of the permanent magnets and a fixing structure ofthe magnets. In this case, generally speaking, such a reinforcementstructure for covering the permanent magnets with a sleeve made of, forexample, carbon fiber or titanium is provided. Japanese Laid-open PatentPublication No. 11-89142, for example, discloses a high speedsynchronous motor provided with ring-shaped magnets including an outercircumference that is reinforced with carbon fiber reinforced plastic(CFRP).

The ring-shaped magnets disclosed in abovementioned Patent Literature 1are under the limitation of upsizing due to a manufacturing restrictionwhich makes it difficult to provide a larger electric motor by which alarger torque is provided. Furthermore, when the ring-shaped magnets arefitted over a magnetic ring and fixed to a rotary shaft with asignificantly large interference for prevention of looseness during ahigh speed rotation, the ring-shaped magnets may crack because ofexpansion of the magnetic ring due to the significantly largeinterference.

On the contrary, an interference arranged to a degree so as not to crackthe ring-shaped magnets does not provide a sufficiently largeinterference to the magnets and the magnetic ring, which presents themagnets and the magnetic ring an idle running, resulting in improperlylow torque in a high speed rotation zone or a failure of a high speedrotation.

Furthermore, in the method disclosed in Patent Literature 1 mentionedabove, the rotator member is fixed to the rotary shaft by a so called an“oil pressure fitting”. Use of this method requires a complicated largemanufacturing apparatus with complex and more difficult operations,which causes a problem of reduced manufacturing efficiency. In addition,the oil pressure fitting requires a hole in the magnetic ring (rotorsleeve) to guide oil pressure from outside to between the magnetic ringand the rotary shaft. However, a high speed rotation operation generatesa stress concentration around the hole, and the maximum stress restrainsthe rotation from reaching the maximum speed. Moreover, the hole has tobe precisely balanced, disposed and formed in consideration of thebalance of the rotary shaft, which leads to a cause of an increasedmanufacturing cost.

Furthermore, the Patent Literature 1 indicates that an oil hole isremoved by machining after a fixation of the rotator member and therotary shaft by oil pressure fitting in order to avoid the stressconcentration. The machining after completion of the rotator, however,is a risky process more than an increase of a simple process, whichrequires an attention to the magnetic attraction of the permanentmagnets during the processing and a possible chemical damage to therotator body itself caused by a cutting liquid. Therefore, such anoperation has a problem of being significantly costly.

Moreover, Patent Literature 1 indicates that the sleeve is expected tohave a fitting force remaining to the rotary shaft even when a rotationspeed of an outer circumference of the rotator member is 250 m/s orhigher. This is intended that the rotator member stably rotates at themaximum speed without looseness, i.e., idle running, of the rotatormember. However, an electric motor used, for example, for a main shaftof a machine tool has such an important performance index that not onlya rotator member does not idle but also how large a cutting toque ispossibly generated. The qualification indicated in Patent Literature 1is not satisfactory as a requirement for the rotator member not to slideat a fixed portion thereof under an application of the cutting loadtorque at the maximum rotation speed. Furthermore, although the similarproblem exists between the magnets and the magnetic ring, PatentLiterature 1 does not indicate any countermeasures thereto.Specifically, with only the fitting force of the sleeve with respect tothe rotary shaft remaining at the maximum rotation speed, there is aproblem that the magnets and the sleeve may slide in the rotationaldirection under increased load.

In consideration of the above-mentioned problems, the present inventionis intended to provide a rotator member and a rotator of a rotaryelectric machine which improves manufacturing efficiency, preventsmagnets from damages during a manufacturing process, increases torqueand output power of a rotary electric machine, and transmits the torqueto a rotary shaft without fail.

SUMMARY OF INVENTION

A rotator member according to a first aspect of the present invention isfixed by press fitting to a rotary shaft of a rotary electric machine.The rotator member includes: a tubular sleeve having a first end at anaxially first side and a second end at an axially second end; aplurality of magnet segments arranged in the circumferential directionat radially outside of the sleeve; and a tubular member covering aplurality of the magnet segments from the outside of the radialdirection to hold the magnet segments between the tubular member and thesleeve. In order to make a press fitting assembly possible, the sleeveis provided with an inner circumference surface that includes a taperedsurface which continuously expands radially outward as extending in adirection from the first end toward the second end. Also, the innercircumference surface of the sleeve does not include a portion where theradius of the inner circumference surface reduces in the direction fromthe first end toward the second end. The magnet segments may beseparated in the circumferential direction, and may be or may not beseparated into a multiple number in the axial direction of the rotaryshaft.

Preferably, the tapered surface of the sleeve is a single linearlytapered surface, or includes a plurality of linearly tapered surfacesconnected each other and inclined with respect to an axis of rotation atdifferent angles from each other. The sleeve has a thick side that has asmaller diameter by the tapered structure. The thick side is preferablyprovided with an end portion to be sufficiently pressed by a press toolduring a press fitting process. The end portion in the sleeve is thusthick, which allows an increased press fitting force to be applied tothe end portion during a press fitting operation. The end portion of thesleeve preferably has a taper angle of 0° such that the end portion hasan inner diameter that is constant.

In a preferable form, the inner circumference surface of the sleeve hasa cylindrical surface of a constant radius extending from the first endtoward the second end over a certain area. The tapered surface includesa linearly tapered surface extending from the cylindrical surface towardthe second end. A gap is preferably formed at least partially betweenthe sleeve and the magnet segments. In addition, the sleeve has an outercircumference that is preferably cylindrical, and each of the magnetsegments has an inner circumference surface that is preferably circulararc. The curvature radius of the inner circumference surface of themagnet segment is larger than the radius of the outer circumferencesurface of the sleeve.

The tapered surface extends preferably from the first end to the secondend. The tapered surface is preferably a linearly tapered surface. Inthis case, the preferable taper ratio of the linearly tapered surface is1/200 to 1/30. Preferably, the sleeve has no holes with openings at theinner circumference surface thereof.

A movement prevention structure is preferably provided between thesleeve and the magnet segments to prevent a relative movement betweenthe sleeve and the magnet segments. The tubular member is preferablycomposed of a material of great specific strength (tensile strength perunit density) including carbon fiber, glass fiber, nonmagnetic metal,aramid fiber, silicon carbide fiber, boron fiber, titanium alloy fiber,ultra high molecular weight polyethylene, or polybutylene terephthalatefiber. Furthermore, such FRP (fiber reinforced plastic) is alsopreferable as a material of the tubular member, that uses carbon fiber,glass fiber, aramid fiber, silicon carbide fiber, boron fiber, titaniumalloy fiber, ultra high molecular weight polyethylene, or polybutyleneterephthalate fiber. A composite material of a combination of any ofthese materials is also preferable. The tubular member may includenonmagnetic metal.

A rotator according to another aspect of the present invention includesa rotary shaft having an outer circumference surface expanding radiallyoutward as extending in a direction from an axially first side toward anaxially second side, and the rotator member described above, in whichthe sleeve is fixed to the rotary shaft on a radially outside of therotary shaft, so that the second end of the sleeve is positioned to theaxially second side of the rotary shaft relative to the first end of thesleeve. Since this structure requires no oil pressure fitting, no holesfor oil are needed in the sleeve. Therefore, it is possible to avoidstress concentration around the holes, thereby advantageously provideincreased maximum rotation speed.

The sleeve is deformed so as to expand radially outward by the rotaryshaft when the rotator member is fixed to the rotary shaft, so that theouter circumference surface of the sleeve and inner circumferencesurfaces of the magnet segments are brought into a pressured contactwith each other. The “pressured contact” means that a relative movementof elements is prevented by a pressing force between the surfacesthereof. However, the relative movement of these elements may be allowedwhen the pressing force is released. In particular, the prevention ofthe relative movement may or may not be maintained when the pressingforce is released.

A substantially entire area (for example, more than 90%) of the innercircumference surface of the sleeve and the outer circumference surfaceof the rotary shaft are brought into a surface-to-surface contact for anaxial distance where the tubular member is disposed. This structureprovides a wider contact area (e.g. a region of more than 90%) betweenthe inner circumference surface of the sleeve and the outercircumference surface of the rotary shaft to thereby reduce the pressingforce between the surfaces, resulting in an easy press fitting operationbetween them. In consideration of convenient disassembling, a minimumgroove may be provided to deliver lubricant oil to their surfaces undercontact. In such a structure, the same value of at least more than 90%may be applied to the area that the surfaces are contacted and fixedwith each other. Preferably, the sleeve deforms beyond its elasticdeformation zone. A rotary electric machine according to another aspectof the present invention includes the rotator described above.

For a rotary electric machine under operation and including the rotatormember being fixed to the rotary shaft, the tubular member is preferablygiven such an interference that fix torque between the sleeve and therotary shaft, and between the magnet segments and the sleeve exceeds themaximum torque of the rotary electric machine at an allowed rotationspeed.

With any stress concentration applied, the maximum rotation speed of therotator is restrained by its limiting stress. Therefore, a structure togenerate stress concentration is preferably excluded. Accordingly, thehole communicating between the outer circumference surface of therotator and the radially inner surface of the rotary sleeve disclosed inthe Patent Literature 1 mentioned above is not preferably provided.Exclusion of the hole avoids stress concentration and can furtherincrease a rotation speed.

A method for manufacturing a rotator member to be press fitted and fixedto a rotary shaft according to another aspect of the present inventionincludes a step of: disposing a plurality of magnet segments in thecircumferential direction on an outer circumference surface of a tubularsleeve that has a first end at an axially first side, a second end at anaxially second side, and an inner circumference surface including atapered surface that continuously expands radially outward as extendingin a direction from the first end toward the second end; and disposing atubular member to cover the plurality of magnet segments from outsidethe radial direction. The step of disposing the tubular member mayinclude directly winding a material of the tubular member around theouter circumference of the magnet segments.

A method for manufacturing a rotator of a rotary electric machineincluding the rotator member manufactured by the method described aboveincludes a step of: providing a rotary shaft that has an outercircumference surface at an area where the rotator member is fixed, theouter circumference surface expanding radially outward as extending in adirection from an axially first side to an axially second side; andfixing the rotator member outside the radial direction of the rotaryshaft by an interference fitting.

The step of fixing the rotator member by an interference fittingincludes fitting the sleeve over the rotary shaft from a side of theaxially first side so that the second end of the sleeve is positioned atthe axially second side relative to the first end; press fitting thesleeve over the rotary shaft so as to push the first end of the sleeveto the axially second side; and causing the sleeve to expand radiallyoutward by the force of press fitting the sleeve, while the sleeve ispress fitted to a predetermined fixing position.

Preferably, the rotator member includes a gap at least partially betweenthe sleeve and the magnet segments. In the step of fixing the rotatormember by the interference fitting, the outer circumference surface ofthe sleeve and the inner circumference surfaces of the magnet segmentsare brought into a surface-to-surface contact in their almost entireareas by causing the sleeve to expand radially outward so as to fill thegap.

Preferably, the outer circumference surface of the sleeve is cylindricaland the inner circumference surface of each magnet segment has acircular arc form. In this case, the inner circumference surface of themagnet segment has a curvature radius that is larger than a radius ofthe outer circumference surface of the sleeve. In the step of fixing therotator member by the interference fitting, the outer circumferencesurface of the sleeve and the inner circumference surfaces of the magnetsegments are brought into a surface-to-surface contact by causing thesleeve to expand radially outward.

BRIEF DESCRIPTION OF DRAWINGS

The abovementioned and other objects, features and advantages of thepresent invention will be further acknowledged with the description ofthe following preferred embodiments with reference to the drawings.

FIG. 1 is a sectional view of an electric motor of an embodimentaccording to the present invention;

FIG. 2 is a sectional view of a rotary shaft illustrated in FIG. 1;

FIG. 3 is a sectional view of a rotator member illustrated in FIG. 1;

FIG. 4 is an external view of the rotator member illustrated in FIG. 1viewed from an axial direction;

FIG. 5 is a sectional view of a sleeve illustrated in FIG. 3;

FIG. 6 is a perspective view of one of magnet segments illustrated inFIG. 3;

FIG. 7 is a perspective view of a tubular member illustrated in FIG. 3;

FIG. 8 is a graph illustrating centrifugal forces acted on the rotaryshaft, the sleeve, and the magnet segments, fix torque between therotary shaft and the sleeve, and fix torque between the sleeve and themagnet segments, all relative to a rotation speed of the electric motor;

FIG. 9 illustrates balance of forces among the tubular member, themagnet segments and the sleeve during a shutdown period of the electricmotor;

FIG. 10 illustrates balance of forces among the tubular member, themagnet segments and the sleeve during a rotation period of the electricmotor;

FIG. 11 is a flowchart illustrating a manufacturing method of therotator member and the rotator according to an embodiment of the presentinvention;

FIG. 12 is a flowchart illustrating a manufacturing method of therotator member and the rotator according to another embodiment of thepresent invention;

FIG. 13 illustrates a step of disposing the magnet segments to thesleeve;

FIG. 14 illustrates the rotator member being assembled;

FIG. 15 is a partially enlarged view of FIG. 14;

FIG. 16 is a sectional view illustrating a step of fixing the rotatormember to the rotary shaft;

FIG. 17 is a partially enlarged sectional view of FIG. 16;

FIG. 18 is a sectional view of the rotator member fixed to the rotaryshaft;

FIG. 19 illustrates the change of the state of the rotator member at astep when the rotator member is fixed to the rotary shaft;

FIG. 20 is an enlarged view of the rotator member according to anotherembodiment;

FIG. 21 is an enlarged view of the rotator member according to furtheranother embodiment;

FIG. 22 is an enlarged view of the rotator member according to stillanother embodiment;

FIG. 23 illustrates the rotator member according to further anotherembodiment; and

FIG. 24 illustrates the rotator member according to still furtheranother embodiment.

DETAILED DESCRIPTION

An embodiment of the present invention will be described below in detailwith reference to the drawing. Firstly, a structure of an electric motor100 according to an embodiment of the present invention will bedescribed referring to FIG. 1. It should be noted that, in the followingdescription, a direction extending along the central axis of a rotaryshaft of the electric motor 100 is designated as an axial direction, andthe left side on the paper of FIG. 1 is designated as an axially frontside while the right side thereon is designated as an axially rear side.It should also be noted, however, that the axially front side and theaxially rear side in the following description are defined for a pointof view of an easy and convenient understanding of the invention, andare not intended to limit the directions, e.g., front side and rearside, of the electric motor.

The electric motor 100 includes a housing 102 that defines an innerspace 101, a stator 110 statically disposed in the inner space 101 ofthe housing 102, and a rotator 400 rotatably disposed radially innerside of the stator 110. The stator 110 includes a stator core 103 andcoil 104 wound over the stator core 103. The stator core 103 is composedof laminated thin plates each made, for example, of an electromagneticplate.

A power line (not illustrated) electrically connected to the coil 104 isextracted from the stator 110, and the power line is connected via athrough hole disposed in the housing 102 to a power source (notillustrated) disposed outside the electric motor 100.

The rotator 400 includes a rotary shaft 200 axially extending in theinner space 101 and a rotator member 300 firmly fixed to outside theradial direction of the rotary shaft 200.

The rotary shaft 200 in this embodiment will be described below withreference to FIG. 2. The rotary shaft 200 is of a tubular configurationhaving a central axis O₁ and a center hole 201 that is concentric withthe central axis O₁. In planning of built-in motor used for a main shaftof a machine tool, the rotary shaft 200 in this embodiment is providedwith the center whole 201. However, the rotary shaft 200 in the presentinvention may be provided with other configurations. Specifically, therotary shaft 200 may be composed of a solid material and may not beprovided with the center hole 201.

The central axis O₁ of the rotary shaft 200 is an axis of rotation ofthe electric motor 100. The rotary shaft 200 is rotatably connected atan axially front side thereof to the housing 102 through a bearing (notillustrated) installed to a front side wall of the housing 102.Similarly, the rotary shaft 200 is rotatably connected at an axiallyrear side thereof to the housing 102 through a bearing (not illustrated)installed to a rear side wall of the housing 102.

The rotary shaft 200 has a tapered outer circumference surface 202 thatexpands radially outward as extending from the axially rear side to theaxially front side. The rotary shaft 200 is provided with anaxially-front-side portion 203 and a step 204 that serve as examples ofstopper members for a manufacturing convenience. The tapered outercircumference surface 202 continuously extends from an axial rear end205 to an axial front end 206. A cylindrical outer circumference surface207 linearly extending in the axial direction is provided at an axiallyrear side of the axial rear end 205 of the tapered outer circumferencesurface 202.

The tapered outer circumference surface 202 may preferably include alinearly tapered surface, i.e., a conical surface. In such aconfiguration, the radius of the tapered outer circumference surface 202increases linearly and gradually from the axial rear end 205 to theaxial front end 206. The tapered outer circumference surface 202 maypreferably include, for example, a linearly tapered surface of a taperedratio of 1/200 to 1/30.

An abutment portion 203 and the step 204 serving as stop members areprovided as a design example for an easier assembly in the manufacturingprocess. The abutment portion 203 has a cylindrical outer circumferencesurface that extends in the axial direction and projects outside theradial direction from the tapered outer circumference surface 202 so asto form the step 204 between the surface 202 and the axial front end206.

Next, the rotator member 300 according to the embodiment will bedescribed below with reference to FIGS. 3 to 7. The rotator member 300includes a tubular sleeve 301, a plurality of magnet segments 311disposed in the circumferential direction outside the radial directionof the sleeve 301, and a tubular member 321 covering the magnet segments311 from outside the radial direction. In response to manufacturing andshaping reasons, the magnet segments 311 may be of a plurality ofseparated form, such that FIG. 3 exemplifies a two separated form in theaxial direction.

As illustrated in FIG. 5, the sleeve 301 is made of a tubular memberwith the center axis O₂ and has a first end 302 at an axially rear sidethereof (i.e., axially first side), a second end 303 at an axially frontside (i.e., axially second side) and a cylindrical outer circumferencesurface 304. The sleeve 301 is provided with a projection part 305 thatprojects radially outward from the outer circumference surface 304. Theprojection part 305 is provided as a design example for easier axialpositioning of the magnets during the manufacturing process.

The sleeve 301 may be made of a magnetic metal material including, forexample, SS400 or S45C. The sleeve 301 has a thickness that maypreferably be arranged thin for an easy press fit operation of thesleeve 301 over the rotary shaft 200. The sleeve 301 may include athickness of 1 mm to 2 mm at the thinnest part thereof. The pressfitting operation of the sleeve 301 over the rotary shaft 200 will bedescribed later.

The sleeve 301 in this embodiment has a tapered inner circumferencesurface 306 (i.e., tapered surface) that continuously expands radiallyoutward as extending from the first end 302 to the second end 303. Thetapered inner circumference surface 306 continuously extends from thefirst end 302 to the second end 303, and does not include a portionwhere the radius thereof reduces in a direction from the first end 302to the second end 303 (i.e., axially frontward direction). In otherwords, the tapered inner circumference surface 306 has a radius thatcontinuously increases in the axially frontward direction between thefirst end 302 and the second end 303 in their entire lengths.

The tapered inner circumference surface 306 may preferably be a linearlytapered surface. In this case, the radius of the tapered innercircumference surface 306 linearly enlarges from a radius R₃ of thetapered inner circumference surface 306 at the first end 302 to a radiusR₄ of the tapered inner circumference surface 306 at the second end 303in a direction from the first end 302 to the second end 303. The radiusR₄ is larger than the radius R₃, i.e., R₄>R₃. The tapered innercircumference surface 306 may preferably be of a linearly taperedsurface of the taper ratio of, for example, 1/200 to 1/30. The range ofthis numeral value will be described later.

The degree of the taper of the tapered inner circumference surface 306is arranged to correspond to the degree of the taper of the taperedouter circumference surface 202 of the rotary shaft 200. Morespecifically, when the same linearly tapered surface is given to thetapered outer circumference surface 202 of the rotary shaft 200 and thetapered inner circumference surface 306 of the sleeve 301, the sametaper ratio (for example, 1/100) is given to the outer circumferencesurface 202 and the inner circumference surface 306.

In the assembled electric motor 100 illustrated in FIG. 1, the sleeve301 is fixed by an interference fitting over the tapered outercircumference surface 202 of the rotary shaft 200 so that the centeraxis line O₁ of the rotary shaft 200 aligns with the center axis line O₂of the sleeve 301. In this configuration, the second end 303 of thesleeve 301 is brought into contact with the step 204 of the abutmentportion 203 serving as a stopper and provided for a convenientassembling. The radius R₄ of the tapered inner circumference surface 306at the second end 303 is substantially the same as a radius of the axialfront end 206 of the tapered outer circumference surface 202.

In addition, the tapered inner circumference surface 306 of the sleeve301 and the tapered outer circumference surface 202 of the rotary shaft200 tightly contact each other with a large surface pressure, so thatthe sleeve 301 is press-pushed outwardly in the radial direction by therotary axis 200. An assembled structure of the sleeve 301 and the rotaryshaft 200 will be described later.

As illustrated in FIG. 6, the magnet segments 311 each are made of amagnet piece of a circular arc form having an inner radius of apredetermined curvature radius. Specifically, the magnet segment 311 hasan axially front end surface 312, an axially rear end surface 313, acircumferentially first end surface 314, a circumferentially second endsurface 315, a radially inner surface 316 and a radially outer surface317. The inner surface 316 of the magnet segment 311 has a circular arcform, while the outer surface 317 may have a curved or flat surface or acombination of the curved and flat surfaces.

In the embodiment illustrated in FIG. 6, although a clear illustrationis given to the surfaces 312, 313, 314 and 315, these surfaces in actualcases may be of a curved surface or an very small surface held between atapered surface and a curved surface and are sometimes vague because ofa reason of a magnetic circuit design or a specification of an electricmotor. In addition, each of the surfaces are defined by edges that arein actual cases chamfered and cut into a curved form, and thus thesurfaces are not defined by pure drawing lines in some cases.

The inner surface 316 has a circular arc form with a predeterminedcurvature radius and extends in the axial direction so as to connect aradially inner side edge of the axially front end surface 312 to aradially inner side edge of the axially rear end surface 313. The outersurface 317 may include a circumferentially smooth curve line toconfigure, for example, a circular arc surface or other curved surfaces.The curvature radius of the inner surface 316 will be described later.

As illustrated in FIG. 7, the tubular member 321 is composed of atube-shaped material extending in the axial direction. Specifically, thetubular member 321 has an axially front end surface 322, an axially rearend surface 323, a tubular inner surface 324 and a tubular outer surface325. In the embodiment of FIG. 7, although the end surfaces 322 and 323are clearly depicted, these end surfaces are sometimes unclearlyobserved due to a material or structure of the tubular member and amanufacturing method thereof.

The tubular member 321 has a durable strength with respect to adeformation force expanding outside the radial direction. In otherwords, the tubular member 321 has a substantially invariable radius(diameter). In addition, the tubular member 321 is preferably made of anonmagnetic material from a point of view of prevention of reducedperformance caused by heat generation or leakage of magnetic flux.Furthermore, the tubular member 321 is preferably small in density forreduced centrifugal force that is generated by rotation.

The tubular member 321 is preferably composed of a material of greatspecific strength (tensile strength per unit density) including carbonfiber, glass fiber, aramid fiber, silicon carbide fiber, boron fiber,titanium alloy fiber, ultra high molecular weight polyethylene andpolybutylene terephthalate fiber. Furthermore, FRP (fiber reinforcedplastic) is also preferable as a material of the tubular member 321,which FRP includes carbon fiber, glass fiber, aramid fiber, siliconcarbide fiber, boron fiber, titanium alloy fiber, ultra high molecularweight polyethylene and polybutylene terephthalate fiber. A compositematerial of a combination of any of these materials is also preferable.Moreover, the tubular member 321 may be composed of austenitic stainlessor nonmagnetic metal including titanium alloy.

In the embodiment illustrated in FIGS. 3 and 4, the assembled rotatormember 300 includes a total of eight magnet segments 311. Specifically,two magnet segments 311 at a circumference position A in FIG. 4 areaxially and adjacently disposed to form a pair. Similarly, two magnetsegments 311 at circumference positions B, C and D in FIG. 4 are axiallyand adjacently disposed to form a pair, respectively.

Accordingly, the rotator member 300 according to the embodiment includesfour pairs of magnet segments 311 that are circumferentially disposed onthe outer circumference surface 304 of the sleeve 301 at substantiallyequal intervals. The magnet segments 311 at the axially rear side areaxially positioned by a structure such as, for example, a projectionpart 305 formed on the sleeve 301.

The tubular member 321 is fitted to cover and surround all the magnetsegments 311 of four circumferential pairs (in total of eight) fromoutside the radial direction of the segments 311. In the assembledelectric motor 100 illustrated in FIG. 1 as described hereinbefore, thesleeve 301 is press-pushed radially outward by the rotary shaft 200.This press-fit force causes the sleeve 301 to deform outside the radialdirection, resulting in pushing each of the magnet segments 311 outsidethe radial direction.

As described above, the tubular member 321, on the other hand, has adurable strength against deformation to expand outside the radialdirection. Therefore, the tubular member 321 upon receiving the pressureapplied from the magnet segments 311 uses its reaction force to push themagnet segments 311 back inside the radial direction.

Such a configuration allows the magnet segments 311 to be firmly heldbetween the sleeve 301 and the tubular member 321. Therefore, thisconfiguration prevents a relative movement of the magnet segments 311with respect to the sleeve 301 and the tubular member 321 even during ahigh speed operation of the rotator member 300 in a driving operation ofthe electric motor 100.

This mechanism will be further described in detail with reference toFIGS. 8 to 10. FIG. 8 illustrates: the centrifugal forces acted on eachmembers; fix torque between the rotary shaft 200 and the sleeve 301; andfix torque between the sleeve 301 and the magnet segments 311, allrelative to the rotation speed of the electric motor 100. The both fixtorque decrease in response to increased rotation speed. The “fixtorque” has such a value that a circumferential friction force betweencontact surfaces of two members is multiplied by a radial distancebetween an axis of rotation and the contact surfaces (i.e., radius ofthe contact surface). A larger fix torque indicates difficulty in arelative circumferential movement (difficulty in slipping) of one memberwith respect to the other member.

In FIG. 8, a line 10 indicates fix torque between the rotary shaft 200and the sleeve 301, while a line 12 indicates fix torque between thesleeve 301 and the magnet segments 311. Furthermore, lines 14, 16 and 18in FIG. 8 indicate centrifugal forces of the magnet segments 311, thesleeve 310 and the tubular member 321, respectively. A line 20 indicatesthe maximum torque of the electric motor 100.

As illustrated in FIG. 8, the fix torque 10 and 12 are considerablylarger than the maximum torque 20 of the electric motor 100 during ashutdown period (i.e., the rotation speed is zero), but decrease inrelation to an increment rotation speed of the electric motor 100 so asto gradually reaching the maximum torque 20.

The maximum torque 20 of the electric motor 100 decreases near 10000min-l due to an example model motor that is fixed to include the maximumoutput power of 90 kW. In general, when the rotation speed is increasedunder constant torque, an output power is considered to increaseendlessly in accordance with the expression (output power of electricmotor=torque×rotation speed), which is not realistic, however, due to alimitation of power supply from a driving power source. Therefore, indesigning electric motors for high speed and high torque, the torque isadapted to decrease from a certain rotation speed to provide a constantoutput power, instead. Accordingly, the torque in this example decreasesnear the point 10000 min-l.

FIGS. 9 and 10 illustrate force balances in a shutdown period and arotation period. For clarity of the drawing and the description, FIGS. 9and 10 principally illustrate the force relationship between magnetsegment 34 and sleeve 36. Although the force relationship between sleeve36 and rotary shaft 37 is not illustrated, a person skilled in the artcould easily understand that the relationship between sleeve 36 androtary shaft 37 could be explained in a similar way as that betweenmagnet segment 34 and sleeve 36.

FIG. 9 illustrates a force balance between the tubular member 32, themagnet segment 34 and the sleeve 36 during a shutdown period of anelectric motor. An arrow 30 in FIG. 9 indicates a force applied from themagnet segment 34 to the sleeve 36. An arrow 26 indicates a reactionforce applied from the sleeve 36 to the magnet segment 34. An arrow 28indicates a friction force between the sleeve 36 and the magnet segment34. The friction force 28 has such a value that the force 26 ismultiplied by a friction coefficient between the sleeve 36 and themagnet segment 34. An arrow 24 in FIG. 9 indicates a force applied fromthe tubular member 32 to the magnet segment 34 (i.e., a compressiveholding force of the tubular member 32). An arrow 22 indicates areaction force applied from the magnet segment 34 to the tubular member32.

Thus, only the force relationship between the magnet segment 34 andsleeve 36 are explained, for clarity of the drawing and the description.However, a person skilled in the art could easily understand that theforce relationship between sleeve 36 and rotary shaft 37 could beexplained in a similar way, except the followings, i.e., a force derivedfrom the interference of the sleeve 36 and a force applied to the sleeve36 from the magnet segment 34 should be added to a force applied torotary shaft 37 from the sleeve 36.

FIG. 10 illustrates force balances among the tubular member 32, themagnet segment 34 and the sleeve 36 during a rotation period of theelectric motor. An arrow 52 in FIG. 10 indicates a force applied fromthe magnet segment 34 to the sleeve 36. An arrow 42 indicates a reactionforce applied from the sleeve 36 to the magnet segment 34. An arrow 48indicates a friction force between the sleeve 36 and the magnet segment34. An arrow 46 indicates a force applied from the tubular member 32 tothe magnet segment 34 (i.e., a compressive holding force of the tubularmember 32). An arrow 54 indicates a reaction force transmitted from thesleeve 36 to the tubular member 32 through the magnet segment 34. Anarrow 38 indicates a total force applied to the tubular member 32. Anarrow 40 in dotted line indicates a centrifugal force acted on themagnet segment 34. A dotted arrow 44 indicates a centrifugal force actedon the tubular member 32.

As illustrated in FIG. 10, the compressive holding force 46 applied bythe tubular member 32 during a rotation period has such a value that thecentrifugal force 44 acted on the tubular member 32 during the rotationperiod is subtracted from the compressive holding force 24 during ashutdown period as illustrated in FIG. 9. Therefore, the tubular member32 is desirable to include light mass and great strength, i.e., highspecific strength. Accordingly, the tubular member 32 is preferably madeof a material that includes carbon fiber as a main component. Thetubular member 32 having light mass is given less reduced compressiveholding force 24 due to centrifugal force, which allows increased forceto hold the magnet segment and the sleeve with further improved rotationspeed.

The force 52 illustrated in FIG. 10 is smaller than the force 30illustrated in FIGS. 9 and 10 because of the centrifugal force 40 of themagnet segment 34 and the centrifugal force 44 of the tubular member 32.This reduces the force 42, and thus the friction force 48 between thesleeve 36 and the magnet segment 34. Accordingly, the fix torque betweenthe sleeve 36 and the magnet segment 34 during a rotation period of theelectric motor 100 is reduced.

Thus, only the force relationship between the magnet segment 34 andsleeve 36 are explained, for clarity of the drawing and the description.However, a person skilled in the art could easily understand that theforce relationship between sleeve 36 and rotary shaft 37 could beexplained in a similar way, except the following, i.e., a force derivedfrom the interference of the sleeve 36 and a force applied to the sleeve36 from the magnet segment 34 should be added to the force applied torotary shaft 37 from the sleeve 36 and the centrifugal force acted onthe sleeve 36 should be taken into consideration. As a result, the fixtorque between the sleeve 36 and the rotary shaft 37 during a rotationperiod of the electric motor 100 is also reduced.

Not only the compressive holding force 46 of the tubular member 32 hasto be remained under the maximum rotation speed of the motor, but alsothe circumferential fix torque between the sleeve 36 and the magnetsegment 34, and between the sleeve 36 and the rotary shaft 37, given bythe compressive holding force 46 has to exceed the maximum torque of themotor at every rotation speed all the time. An allowance of more thanfive times the maximum torque of the motor is preferable.

Therefore, for the rotator member 300 in this embodiment, aninterference of the tubular member 321 is set such that the fix torquebetween the sleeve 301 and the rotary shaft 200 exceeds the maximumtorque of the rotary electric machine 100, and the fix torque betweenthe magnet segments 311 and the sleeve 301 exceeds the maximum toque ofthe electric motor 100, both in a full range in which the rotaryelectric machine 100 is operable.

With such an arrangement, as illustrated in FIG. 8, the fix torque 10between the rotary shaft 200 and the sleeve 301 and the fix torque 12between the sleeve 301 and the magnet segment 311 exceed the maximumtorque 20 of the electric motor 100 at any rotation speed of theelectric motor 100. This prevents the relative movement between therotary shaft 200 and the sleeve 301, and between the sleeve 301 and themagnet segment 311 in a driving operation of the electric motor 100.

Next, an operation of the electric motor 100 will be described withreference to FIGS. 1 to 7. Upon receiving a current from a power sourceoutside the electric motor 100 to a coil 104 via a power line, thestator 110 generates a rotating magnetic field around the central axisO₁. The rotating magnetic field generated by the stator 110 applies anelectromagnetic force to the magnet segments 311 of the rotator member300 in the circumferential direction. Accordingly, the rotator member300 rotates integrally with the rotary shaft 200.

Next, a manufacturing method for the rotator member 300 according to theembodiment of the present invention will be descried below withreference to FIGS. 11 to 19. The manufacturing method S10 for therotator member 300 includes step S1 to step S5. Specifically, in thestep S1 the sleeve 301 is provided. For example, machining is applied toinner and outer circumference surfaces of a tubular material to form thetapered inner circumference surface 306 and the tapered outercircumference surface 304. Furthermore, if need be, the projection part305, for example, is formed for convenience of an assembling process.The radius R₄′ of the tapered inner circumference surface 306 at thesecond end 303 of the sleeve 301 provided in the step S1 is smaller thanthe radius R₄ in the assembled electric motor 100 (refer to FIG. 17).Similarly, the radius R₃′ of the tapered inner circumference surface 306at the first end 302 of the sleeve 301 provided in the step S1 issmaller than the radius R₃ in the assembled electric motor 100.

In the step S2 the magnet segments 311 are provided. Specifically, eightmagnet segments 311 are provided each of which has a substantiallycircular arc configuration and is provided with the inner surface 316having a predetermined curvature radius. In the step S3 the tubularmember 321 is provided. The material of the tubular member 321 ispreferably of great specific strength (tensile strength per unitdensity) that includes carbon fiber, glass fiber, aramid fiber, siliconcarbide fiber, boron fiber, titanium alloy fiber, ultra high molecularweight polyethylene and polybutylene terephthalate fiber. Furthermore,any one of FRP (fiber reinforced plastic) including abovementionedmaterial(s), austenitic stainless or titanium, nonmagnetic metal such astitanium alloy is preferable, and a composite material thereof is alsopreferable.

The step S1 to the step S3 may be carried out concurrently or in anyorder. In addition, the step S1 to the step S3 may be carried out inrespective manufacturing locations, or at least two steps among thesteps S1 to S3 may be carried out at the same manufacturing location.

In the step S4 total of eight magnet segments 311 are disposed on theouter circumference surface 304 of the sleeve 301. This step S4 will bedescribed below with reference to FIG. 13. First, two magnet segments311 provided in the step S2 are adjacently placed in the axial directionat a circumference position A to form a pair and are placed on the outercircumference surface 304 of the sleeve 301. Similarly, two magnetsegments 311 are adjacently placed in the axial direction at each ofcircumference positions B, C and D to make a pair and are placed on theouter circumference surface 304 of the sleeve 301.

The pair of magnet segments 311A at the circumference position A hassuch a high magnetic field that a side of the inner surface 316 resultsin a south pole and a side of the outer surface 317 results in a northpole. On the other hand, the pair of magnet segments 311B at thecircumference position B has such a magnetic field that a north pole isgiven to a side of the inner surface 316 while a south pole is given toa side of the outer surface 317.

Furthermore, the pair of magnet segments 311C at the circumferenceposition C has such a magnetic field that a south pole is given to aside of the inner surface 316 while a north pole is given to a side ofthe outer surface 317. In the similar manner, the pair of magnetsegments 311D at the circumference position D has such a magnetic fieldthat a north pole is given to a side of the inner surface 316 while asouth pole is given to a side of the outer surface 317.

In summing up, the pairs of the magnet segments 311A to 311D in thisembodiment are arranged in the circumferential direction such that thesouth pole and the north pole thereof alternate in the circumferentialdirection. It is preferable that the magnet segments 311 in thisembodiment are magnetized prior to the step S4. This allows the pairs ofthe magnet segments 311 to draw with one another in a magnetic fieldgenerated by the magnet segments 311, resulting in an easy positioningoperation of the magnet segments 311 on the outer circumference surface304 of the sleeve 301.

In the step S5 the tubular member 321 is disposed so as to cover themagnet segments 311 from outside the radial direction. Specifically, thetubular member 321 provided in the step S3 is fitted outside the radialdirection of the magnet segments 311 in such a manner that the innersurface 324 of the tubular member 321 faces the outer surfaces 317 ofoutside each radial direction of the magnet segments 311. At this stage,the tubular member 321 and the magnet segments 311 may be of a loosefitting or a small degree of interference fitting. For the interferencefitting, only a little interference for prevention of fall off of thetubular member 321 is sufficient.

FIG. 12 illustrate another embodiment of the manufacturing method of therotator member 300. In place of the step S3 in FIG. 11, in the step S5,the tubular member 321 may be disposed on the magnet segments 311 bydirectly winding a material of the tubular member 321 around the outercircumference of the magnet segments 311 (step S3′). For example, amaterial in the form of string, belt, or sheet may be used to cover theouter circumference of the magnet segments 311 to form a certainthickness of a wound layer resulting from a number of windings of thematerial in the rotational direction around the outer circumference ofthe magnet segments 311.

In this embodiment, the radius of the inner surfaces 316 of the magnetsegments 311 is set to be larger than the outer circumference surface304 of the sleeve 301. Specifically, as illustrated in FIG. 15, R₇ islarger than R₈ (R₇>R₈), wherein R7 is the curvature radius of the innersurfaces 316 of the magnet segments 311 and R8 is the radius of theouter circumference surface 304 of the sleeve 301.

Such an arrangement provides gap 330 between the inner surfaces 316 ofthe magnet segments 311 and the outer circumference surface 304 of thesleeve 301 at circumferential end zones of the inner surfaces 316 of themagnet segments 311. The gap 330 includes a function that will bedescribed later.

If the outer circumference of the magnet segment 311 is not circular,the tubular member 321 may be deformed along the outer circumference ofthe magnet segment 311 with a press fitting process to allow asurface-to-surface contact between the outer surface of the segment 311and the inner surface of the tubular member 321 to thereby integrallyassemble the two members.

With the tubular member 321 fitted over a radially outside of the magnetsegments 311, it becomes possible to provide the rotator member 300 asan integrated member in which the magnet segments 311 are held betweenthe sleeve 301 and the tubular member 321.

With the step S1 to the step S5, the rotator member 300 illustrated inFIG. 14 is produced. Since the rotator member 300 is pre-produced as anintegrated member, an easy transportation of the rotator member 300 isaccomplished. In the field of a built-in electric motor, for example, anassembly of such a rotator member is manufactured as a single productand distributed, in some cases. The rotator member 300 according to theembodiment has a general structure and is easy to handle, which isadvantageous in this technical field from a point of view ofdistribution.

Below, the manufacturing method for the rotator according to anembodiment of the present invention will be further described withreference to FIG. 11. The method S20 for manufacturing the rotatorincludes step S6 to step S8. Specifically, in the step 6 the rotaryshaft 200 illustrated in FIG. 2 is provided. For example, the taperedouter circumference surface 202 is formed by machining of an outercircumference surface of a tubular member. Before or after theabovementioned process, the cylindrical outer circumference surface 207and the abutment portion 203 may be formed as necessary.

In the step S7, the rotator member 300 provided in the step S5 is fittedfrom an axially rear side of the rotary shaft 200. This step S7 will bedescribed with reference to FIGS. 16 and 17. First, the sleeve 301 ofthe rotator member 300 is fitted from a side of the second end 303 tothe axially rear end of the rotary shaft 200 provided in the step S6.

The rotary shaft 200 is held so that an end surface (not illustrated) ofan axially second side (front side) thereof is pushed toward an axiallyfirst side (rear side), while the end 302 of the sleeve 301 of therotator member 300 is pushed toward the axially front side. In otherwords, the rotator member 300 is pushed in the axially frontwarddirection as illustrated by an arrow E in FIG. 16.

This causes a front end of the tapered inner circumference surface 306of the sleeve 301 to contact the tapered outer circumference surface 202of the rotary shaft 200 at a contact point P. This state is depicted inFIG. 16. It is preferable that as illustrated in FIG. 17, the radius ofthe tapered outer circumference surface 202 at the point P is equal tothe radius R₄′ of the tapered inner circumference surface 306 of thesecond end 303 of the sleeve 301 provided in the step S1.

In the step S8 the rotator member 300 is further press-pushed in theaxially frontward direction over the rotary shaft 200. Morespecifically, the rotator member 300 is press-pushed in the axiallyfrontward direction to a certain position, e.g. to the position untilthe second end 303 of the sleeve 301 is brought into contact with thestep 204 of the abutment portion 203, as illustrated in FIG. 17.

The sleeve 301 expands radially outward for a difference δ between theradius R₁ and the radius R₄′, as moving axially frontward for a distancex from the contact point P to the step 204. As a result, the rotatormember 300 in this state is fixed by an interference fitting to therotator shaft 200 with an interference of φ2δ. It is preferably notedthat the sleeve 301 in this state may be deformed beyond its elasticdeformation zone.

The sleeve 301 expands radially outward by the press-pushing forceapplied to the sleeve 301 until the sleeve 301 reaches the predeterminedfixing position, which causes the magnet segments 311 to move outsidethe radial direction. With such a movement, the tubular member 321receives a force applied in the outer direction and thus similarlyexpands outside the radial direction. Accordingly, the tubular member321 stores an elastic compressive force that hold the magnet segments311 and the sleeve 301 between the tapered outer circumference surface202 of the rotary shaft 200 and the tubular member 321, generatingpressing forces (surface pressing forces) between the surfaces incontact. The pressing forces firmly fix, against a movement in thecircumferential direction, the magnet segments 311 to the outercircumference surface 304 of the sleeve 301, and the inner circumferencesurface 306 of the sleeve 301 to the tapered outer circumference surface202 of the rotary shaft 200.

It is preferably noted that the inner circumference surface 306 of thesleeve 301 is brought into a surface-to-surface contact with the taperedouter circumference surface 202 of the rotary shaft 200 in almost all ofthe area (more than 90%) between the axially front end surface 322 ofthe tubular member 321 and the axially rear end surface 323 thereof.

Specific dimensions of the rotary shaft 200 and the sleeve 301 arepresented below as an example. The taper ratio of both the tapered outercircumference surface 202 of the rotary shaft 200 and the tapered innercircumference surface 306 of the sleeve 301 is set to 1/100. Thethickness of the sleeve 301 at the second end 303 of is set to 1 mm, andthe axial length of the sleeve 301, i.e., the distance between the firstend 302 and the second end 303, is set to 100 mm.

Therefore, the thickness of the sleeve 301 at the first end 302 resultsin 1.5 mm. In this case, when the diameter of the outer circumferencesurface 304 of the sleeve 301 is set to φ80 mm (i.e., the radius is 40mm), the diameter of the tapered inner circumference surface 306 of thesecond end 303 results in φ78 mm (i.e., R4=39 mm), and the diameter ofthe tapered inner circumference surface 306 of the first end 302 resultsin 977 mm (i.e., R3=38.5 mm).

On the other hand, when the outer diameter of the axial end 206 of therotary shaft 200 is arranged at φ78.5 mm (i.e., R1=39.25 mm), and theouter diameter of the tapered outer circumference surface 202 of therotary shaft 200 at a position 100 mm axially rearward from the axialfront end 206 results in φ77.5 mm (i.e., the radius is 38.75 mm).

In this case, when the sleeve 301 is press-fitted over the rotary shaft200 so that the second end 303 of the sleeve 301 contacts the step 204of the rotary shaft 200, the sleeve 301 and the rotary shaft 200 arefixed with each other by an interference fitting of an interference ofφ0.5 mm.

With completion of the step S8, the rotator member 300 is fixed to therotary shaft 200 by an interference fitting, whereby a rotator 400illustrated in FIG. 18 is produced. Thus, the step S7 and the step S8compose a step S9 in which the rotator member 300 is fixed outside theradial direction to the rotary shaft 200 by an interference fitting.

As described above, in this embodiment the magnet segments 311 aredisposed in the circumferential direction, and the curvature radius R₇of the inner circumference surface 316 of each magnet segment 311 is setto be larger than the curvature radius R₈ of the outer circumferencesurface 304 of the sleeve 301. This prevents cracks of the magnetsduring the preparation of the rotator 400.

FIG. 19 illustrate the prevention of cracks of the magnets, which willbe described below. Section (a) of FIG. 19, corresponds to FIG. 15, andillustrates the rotator member 300 before press-fitted over the rotaryshaft 200. Section (b) of FIG. 19, corresponds to FIG. 4, andillustrates the rotator member 300 after press-fitted over the rotaryshaft 200.

As described previously, the gap 330 is formed between the innercircumference surfaces 316 of the magnet segments 311 and the outercircumference surface 304 of the sleeve 301 prior to the press-fittingof the rotator member 300 over the rotary shaft 200. When the rotatormember 300 is press fitted over the rotary shaft 200 in the step S8, therotator member 300 expands radially outward by the above difference 8.

As illustrated in section (b) of FIG. 19, the sleeve 301 expandsradially outward so as to fill the gap 330, resulting in asurface-to-surface contact between the outer circumference surface 304of the sleeve 301 and inner circumference surfaces 316 of the magnetsegments 311. The gap 330 is formed due to the difference between thecurvature radius R₇ of the inner circumference surfaces 316 of themagnet segments 311 and the radius R₈ of the outer circumference surface304 of the sleeve 301. The size of the gap 330 is determined based onthe expansion of the sleeve 301 in the step S8.

According to the configuration described above, the gap 330 functions asan “allowance” to allow expansion of the sleeve 301 and preventsapplication of excessive force from the sleeve 301 to the magnetsegments 311 in the step S8, thereby cracks in the magnet segments 311are prevented.

In this embodiment, the magnet segments 311 are composed of four pairsthat are separately arranged in the circumferential direction, and arenot continuous in a form of a ring. Such an arrangement can successfullyprevent damages in the magnet segments 311 in the step S8 when a forceis applied to the magnet segments 311, compared to the magnet in a formof a ring. In addition, with an adjustment of a size and a number of themagnet segments 311 to be used, an application of the segments 311 to alarge size electric motor can be easily carried out.

According to the embodiment, as mentioned above, the sleeve 301 expandsoutside the radial direction so as to fill the gap 330, which allows asurface-to-surface contact between the outer circumference surface 304and the inner circumference surfaces 316 of the magnet segments 311 inthe step S8. This configuration permits the outer circumference surface304 of the sleeve 301 and the inner circumference surfaces 316 of themagnet segments 311 to be firmly and tightly attached with each otherwith a pressing force evenly distributed between them in the rotator 400with the assembly completed. Such a structure increases a friction force(fix torque) between the outer circumference surface 304 of the sleeve301 and the inner circumference surfaces 316 of the magnet segments 311to thereby efficiently prevent a relative movement of the magnetsegments 311 with respect to the sleeve 301 in a driving operation ofthe electric motor 100.

Furthermore, in this embodiment the tapered surfaces 202 and 306 areused to expand the sleeve 301 to press fit the rotator member 300 overthe rotary shaft 200 in the step S8. Such an arrangement allows uniformand highly precise expansion of the sleeve 301 to thereby stably holdthe magnet segments 311 between the sleeve 301 and the tubular member321, which enables the rotator 400 to include a firm structure, allowingthe rotator 400 to be used in a motor for a product operated under ahigh rotation speed.

Moreover, in this embodiment, the process of press fitting the rotatormember 300 over the rotary shaft 200 only requires a press machine forpushing the rotator member 300 in an axially one direction, and does notrequire any other complicated machines, which enables providing improvedproductivity and a decreased manufacturing cost.

According to the embodiment, there is no need to use a so-called“thermal insert” method which requires heating of the rotator member 300and member of the rotary shaft 200 for press fitting. Therefore,high-temperature demagnetization of the magnets caused by heating withis prevented.

Since the “thermal insertion” is excluded in this embodiment, therotator member 300 can be firmly fixed to the rotary shaft 200 eventhough a material with a small linear expansion coefficient such ascarbon fiber, titanium or glass fiber is used.

Furthermore, according to the embodiment, with a proper adjustment ofthe degree (taper ratio, inclined angle with respect to the axialdirection) of the tapered surfaces 202 and 306, it becomes possible toreadily and freely determine an interference between the sleeve 301 andthe tubular member 321. Therefore, application of the rotator member 300to electric motors of various types and sizes is possible.

It is preferably noted that the tapered outer circumference surface 202and the tapered inner circumference surface 306 may preferably beprovided with the taper ratio in a range between 1/1000 and 1/30. Thisrange of value will be described below. When the sleeve 301 is pressfitted over the rotary shaft 200 with the taper ratio of the upper limit(1/30), an elastic compressed force is applied inside the radialdirection from the sleeve 301 to the rotary shaft 200. Just after thesleeve 301 is press fitted over the rotary shaft 200, the elasticcompressed force acts to cause the sleeve 301 to move to draw from therotary shaft 200 along the tapered outer circumference surface 202.

Consequently, the inventor of the present invention found out as aresult of examination tests that the taper ratio arranged larger than1/30 (for example, 1/10, 1/5) would adversely present the problems to befollowed. Specifically, when the sleeve 301 is press fitted over therotary shaft 200, the force of the sleeve 301 to draw from the rotaryshaft 200 tends to exceed a friction force between the sleeve 301 andthe rotary shaft 200. This would highly result in a drop off of thesleeve 301 from the rotary shaft 200.

In addition, with the taper ratio larger than 1/30, a substantiallylarge force is involved to press fit the sleeve 301 over the rotaryshaft 200, which would require a larger manufacturing machine. From sucha point of view, it is preferable to arrange the taper ratio with themaximum value of 1/30.

Regarding to the taper ratio of the minimum value (1/1000) on thecontrary is such that with the taper ratio smaller than 1/1000, there ispreferable a larger axial distance (the distance x mentioned previously)to obtain a predetermined interference (φ0.5 mm in the example mentionedabove) in the press fitting between the sleeve 301 and the rotary shaft200. This deteriorates operational efficiency. Furthermore, the taperratio smaller than 1/1000 may result in machining errors in an actualmanufacturing process. From such a point of view, the minimum value ofthe taper ratio is preferably 1/1000. From the abovementioned point ofview, the minimum value of the taper ratio is more preferably around1/200 with a consideration of an actual manufacturing cost. Such aminimum value allows turning and cutting operations.

In another embodiment of the present invention, movement preventionstructure may be provided between the sleeve 301 and the magnet segments311 to prevent a relative movement between the sleeve 301 and the magnetsegments 311. This structure will be described with reference to FIGS.20 to 22. Reference numerals that are same as in the embodimentdescribed above are applied to similar members with an exclusion of thedescriptions thereof.

First, a rotator member 500 according to another embodiment of thepresent invention will be described below with reference to FIG. 20.Section (a) of FIG. 20, corresponding to section (a) of FIG. 19,illustrates a rotator member 500 to be press fitted over the rotaryshaft 200. Section (b) of FIG. 20, corresponds to section (b) of FIG.19, illustrates the rotator member 500 press fitted over the rotaryshaft 200.

The rotator member 500 in this embodiment includes a movement preventionstructure 501 on the outer circumference surface 304 of the sleeve 301.The movement prevention structure 501 is provided to prevent a relativemovement of the sleeve 301 with respect to the magnet segments 311, andis configured to increase a friction coefficient between the sleeve 301and the magnet segments 311. The movement prevention structure 501 mayinclude, for example, a high frictional resin coating layer, an adhesiveresin coating layer, a layer applied with a sandblast process, a coatinglayer including material for improvement of a friction coefficient, anda layer applied with a chemical surface process for improvement of afriction coefficient.

The movement prevention structure 501 may be made of a protrusionextending outside the radial direction from the outer circumferencesurface 304 of the sleeve 301. In this case, the magnet segment 311 mayinclude on the inner circumference surface 316 an engaging portion forengagement with the protrusion. When the movement prevention structure501 is made of a coating layer, the thickness thereof may preferably be0.01 mm to 0.1 mm.

When the movement prevention structure 501 is made of the protrusionextending outside the radial direction from the outer circumferencesurface 304 of the sleeve 301, the height of the protrusion maypreferably be 0.5 mm or higher and 1/3 or less of the thickness of themagnet segments 311. The process of providing the movement preventionstructure 501 on the outer circumference surface 304 of the sleeve 301may be carried out in the step S1 with the cutting operation of theouter circumference surface 304 of the sleeve 301, or may be carried outin the step S4 prior to the positioning of the magnet segments 311 overthe sleeve 301.

As illustrated in section (b) of FIG. 20, when the sleeve 301 isexpanded outside the radial direction by an interference with respect tothe rotary shaft 200 so as to fill the gap 330, the outer circumferencesurface 304 of the sleeve 301 and the inner circumference surfaces 316of the magnet segments 311 together make a surface-to-surface contactover the movement prevention structure 501. Prior preparation of the gap330 prevents cracks in the magnet segments 311 due to the expansion ofthe sleeve 301 in the radial direction.

With the surface-to-surface contact between the outer circumferencesurface 304 of the sleeve 301 and the inner circumference surfaces 316of the magnet segments 311, a relative movement of the magnet segments311 with respect to the sleeve 301 and the tubular member 321 during ahigh speed rotation of the rotator member 500 in a driving operation ofthe electric motor 100 is effectively prevented.

A rotator member 510 according to a further embodiment of the presentinvention will be described with reference to FIG. 21. Section (a) ofFIG. 21, corresponding to section (a) of FIG. 19, illustrates a rotatormember 510 to be press fitted over the rotary shaft 200. Section (b) ofFIG. 21, corresponding to section (b) of FIG. 19, illustrates therotator member 510 fitted over the rotary shaft 200.

The rotator member 510 in this embodiment includes a movement preventionstructure 511 provided on the inner circumference surface 316 of thecorresponding magnet segment 311. Similarly, this movement preventionstructure 511 is configured to increase a friction coefficient betweenthe sleeve 301 and the magnet segment 311. The movement preventionstructure 511 may be a protrusion extending radially inwardly from theinner circumference surface 316 of the magnet segment 311.

As illustrated in section (b) of FIG. 21, as the sleeve 301 expandsoutside the radial direction so as to fill the gap 330, the outercircumference surface 304 of the sleeve 301 and the inner circumferencesurface 316 of the magnet segment 311 make a surface-to-surface contactwith each other via the movement prevention structure 511. Such aconfiguration effectively prevents a relative movement of the magnetsegment 311 with respect to the sleeve 301 and the tubular member 321during a high speed rotation of the rotator member 510 in a drivingoperation of the electric motor 100.

The process of providing the movement prevention structure 511 on theinner circumference surface 316 of the magnet segment 311 may be carriedout in the step S2 with the preparation of the magnet segments 311, orcarried out in the step S4 prior to the installation of the magnetsegments 311 on the sleeve 301.

A rotator member 520 according to still another embodiment of thepresent invention will be described with reference to FIG. 22. Section(a) of FIG. 22, corresponding to section (a) of FIG. 19, illustrates arotator member 520 to be press fitted over the rotary shaft 200. Section(b) of FIG. 22, corresponding to section (b) of FIG. 19, illustrates therotator member 520 fitted over the rotary shaft 200.

The movement prevention structure 521 in the rotator member 520according to this embodiment is independently formed and insertedbetween the sleeve 301 and the corresponding magnet segment 311. Themovement prevention structure 521 has a significant friction coefficientwith respect to the sleeve 301 and the magnet segment 311. The movementprevention structure 521 may be composed, for example, of a frictionsheet with a process on the surface thereof for improvement of afriction coefficient, an adhesive sheet with an adhesive on the surfacethereof, or a rubber sheet made, for example, of NBR or silicon providedwith a tacking performance. The movement prevention structure 521preferably has a thickness of 0.03 mm to 0.1 mm.

As illustrated in section (b) of FIG. 22, the expansion of the sleeve301 outside the radial direction fills the gap 330, thereby creating asurface-to-surface contact between the outer circumference surface 304of the sleeve 301 and the inner circumference surface 316 of the magnetsegment 311 via the movement prevention structure 521. Due to thisconfiguration, the magnet segments 311 do not move with respect to thesleeve 301 and the tubular member 321 during a high speed rotation ofthe rotator member 520 in a driving operation of the electric motor 100.

Although the above embodiment is described based on the magnet segmentsof a circular arc form provided with a certain curvature radius, themagnet segments may include other types of shapes. Such a configurationwill be described with reference to FIG. 23.

FIG. 23 illustrates a rotator member 600 according to still anotherembodiment of the present invention, wherein section (a) of FIG. 23 isan external view of the rotator member 600 viewed from the axialdirection, and section (b) of FIG. 23 is a partial enlarged view ofsection (a).

The rotator member 600 includes a sleeve 601, multiple magnet segments611 disposed outside the radial direction of the sleeve 601, and atubular member 321 covering the magnet segments 611 from a radiallyoutside.

The sleeve 601 in this embodiment includes concave 602 inwardlyrecessing from an outer circumference surface 604. The concave 602axially extend from one axial end of the sleeve 601 to the other axialend thereof, and each of which is defined by a bottom surface of asubstantially flat plane and circumference end surfaces uprising fromthe respective circumference ends of the bottom surface. The concave 602are circumferentially disposed on the outer circumference surface 604with regular intervals. A convex 603 is provided between two adjacentconcave 602 so as to project outside the radial direction from thebottom surface of the concave 602.

The magnet segments 611 each include an inner circumference surface 616at a radially inner side thereof and an outer circumference surface 617at a radially outer side thereof. In this embodiment the outercircumference surface 617 of the magnet segment 611 has a curved surfacelike in the above-mentioned embodiment, while the inner circumferencesurface 616 of the magnet segment 611 has a substantially flat surface.

As depicted in FIG. 23, in the assembled rotator member 600, the magnetsegments 611 are stored in the respective concave 602 formed in thesleeve 601 so as to allow surface-to-surface contacts between the innercircumference surfaces 616 of the magnet segments 611 and the bottomsurfaces of the concave 602. The convexes 603 circumferentially disposedat both sides of the respective concave 602 prevent circumferencemovement of the magnet segments 611.

Each of the concave 602 may include axial end surfaces uprising from twoaxial ends of the bottom surface the concave 602. In this case, themagnet segments 611 are prevented from moving in the axial direction bythe axial ends of the concave 602.

According to this embodiment, the operation of positioning the magnetsegments 611 on the radial outer side of the sleeve 601 in the step S4becomes easier. In addition, it becomes possible to prevent a relativemovement of the magnet segments 611 with respect to the sleeve 601 in adriving operation of the electric motor in which the rotator member 600is employed.

A rotator member 700 according to still another embodiment of thepresent invention will be described with reference to FIG. 24. It ispreferable that, like in the abovementioned embodiment, the samereference numerals are applied to similar elements with the descriptionthereof being omitted. The rotator member 700 includes a tubular sleeve701, a plurality of magnet segments 311 disposed outside the radialdirection of the sleeve 301, and a tubular member 321 covering themagnet segments 311 from outside the radial direction.

The sleeve 701 is made of a tubular member having a center axis line O₂,and includes a first end 702 at an axially rear side (i.e., axial firstside), a second end 703 at an axially front side (i.e., axial secondside), and a cylindrical outer circumference surface 704 extending inthe axial direction. The sleeve 701 has a protrusion 705 projectingoutside the radial direction from the outer circumference surface(cylindrical surface) 704 at the axially rear end thereof. Theprotrusion 705 is an example for easy arrangement of the magnets in theaxial direction during a manufacturing process.

The sleeve 701 includes a cylindrical surface 704 extending radiallyfrontwardly from the first end 702, a tapered inner circumferencesurface 705 and a tapered inner circumference surface 706 bothcontinuously expanding outside the radial direction toward an axiallyfrontward direction. The radius of the cylindrical surface 704 isconstant in the direction from the first end 702 toward the second end703.

The first tapered inner circumference surface 705 is a conical surfacethat extends from an axially frontward end edge 704A of the cylindricalsurface 704 and has a first inclined angle θ₁ inclined with respect tothe axis O₂. The second tapered inner circumference surface 706 is aconical surface that extends from an axially frontward end edge 705A ofthe first tapered inner circumference surface 705 to the axially frontend of the second end 703 and has a second inclined angle θ₂ inclinedwith respect to the axis O₂. The first angle θ₁ is arranged to besmaller than the second angle θ₂.

As described above, the present invention uses the permanent magnetsegments that are not ring-shaped but separated at least in thecircumferential direction. In fixing the sleeve to the rotary shaft, thetapered surfaces are used to expand the sleeve for a press fit over therotary shaft. This can provide the sleeve and the tubular member withinterference larger than interference by a thermal insert, which allowsfirm fixations of the magnet segments and the sleeve with respect to therotary shaft. Since the magnet segments are separated in thecircumferential direction, the magnet segments do not crack even under alarge interference, whereby the magnet segments are firmly held betweenthe sleeve and the tubular member. This further strengthens thestructure of the rotator member. As a result, the rotator member can beapplied to a rotary electric machine operated at a higher rotationspeed.

In addition, the process of fixing the sleeve to the rotary shaft can besimplified, excluding use of complicated manufacturing machines.Therefore, it is possible to provide improved manufacturing efficiencyand a reduced manufacturing cost.

Since the magnet segments are separated in the circumferentialdirection, any cracks in the magnet segments due to an expansion of thesleeve in the radial direction in a process of fixing the sleeve to therotary shaft are effectively prevented. Therefore, no cracks in themagnets are found even under a fixation between the rotator member andthe rotary shaft with a larger interference. Accordingly, the rotatormember can be operated under a higher rotation speed compared to anyconventional rotator members.

The magnet segments separated in the circumferential direction allows aneasy production of the magnet segments and a utilization of relativelylarge magnet segments. With the use of the larger magnet segments, itbecomes possible to manufacture a rotary electric machine with largertorque that is not obtained by a magnet in a form of a ring.Accordingly, the present invention can rotate a rotary electric machinewith larger torque and higher rotation speed, so that a rotary electricmachine with higher output power can be provided.

Moreover, although the embodiment described above has eight magnetsegments disposed in the circumferential direction, any number of magnetsegments can be provided under such a condition that two or more magnetsegments are disposed in the circumferential direction. In addition, twoneighboring magnet segments may be provided with a gap between them, ormay be in contact with each other.

The tapered outer circumference surface of the rotary shaft and thetapered inner circumference surface of the sleeve may include a taperedsurface whose curvature radius changes in the axial direction like atapered surface of an exponential function, besides the linear taperedsurface.

In the embodiment described above, although the tubular member is pressfitted on the radially outside of the magnet segments 311 (step S5), amaterial in a form of a sheet, belt, string or thread may be wounded onthe radially outside of the magnet segments 311 to assemble the rotatormember 300.

Furthermore, although the above embodiment describes the presentinvention that is applied to an electric motor, the present inventioncan be properly applied to any rotary electric machines including agenerator.

The present invention has been described above through the embodiments,which, however, do not intend to limit the scope of the invention setforth in the claims. Furthermore, not all of the combinations of thefeatures described in the embodiments intend to be in need of thefeatures or methods of the present invention. Moreover, it would beobvious for a person skilled in the art to be able to modify or revisethe embodiments described above. It would be obvious from thedescription of the claims that any embodiments with such modification orrevision would be included in the technical scope of the presentinvention.

It is preferable that an execution procedure in each process includingmotions, processes, steps and stages in the devices, systems, programsand methods described in the claims, the description and the drawing donot specify “before” or “prior to”, and thus they can be carried out inany desired order, unless a preceding output is used in a followingprocess. As a matter of convenience, although terms such as “first” and“next” may be used in any of the claims, the description and the actionflows in the drawing, they do not intend to specify any execution order.

1. A rotator member to be fixedly press fitted to a rotary shaft of arotary electric machine, the rotator member comprising: a tubular sleevehaving a first end at an axially first side and a second end at anaxially second side; a plurality of magnet segments arranged in thecircumferential direction at radially outside of the sleeve; and atubular member adapted to cover the magnet segments from a radiallyouter side to hold the magnet segments between the tubular member andthe sleeve, wherein the sleeve has an inner circumference surface thatincludes a tapered surface, the tapered surface continuously expandingradially outward as extending in a direction from the first end towardthe second end, wherein the inner circumference surface of the sleevedoes not include a portion where the radius of the inner circumferencesurface reduces in the direction from the first end toward the secondend.
 2. The rotator member of claim 1, wherein the tapered surface ofthe sleeve is a linearly tapered surface, or includes a plurality oflinearly tapered surfaces connected each other and inclined with respectto an axis of rotation at different angles from each other.
 3. Therotator member of claim 1, wherein the inner circumference surface ofthe sleeve has a cylindrical surface of a constant radius extending fromthe first end toward the second end, wherein the tapered surfaceincludes a linearly tapered surface extending from the cylindricalsurface toward the second end.
 4. The rotator member of claim 1, whereinthe linearly tapered surface has a taper ratio of 1/200 to 1/30.
 5. Therotator member of claim 1, wherein the sleeve does not include a holewith an opening at the inner circumference surface of the sleeve.
 6. Therotator member of claim 1, wherein a gap is formed at least partiallybetween the sleeve and the magnet segments.
 7. The rotator member ofclaim 1, wherein the outer circumference surface of the sleeve iscylindrical, wherein the inner circumference surface of each of themagnet segments is circularly arc and has a curvature radius that islarger than a curvature radius of the outer circumference surface of thesleeve.
 8. The rotator member of claim 1 further comprising a movementprevention structure for prevention of a relative movement between thesleeve and the magnet segments.
 9. The rotator member of claim 1,wherein the tubular member includes: carbon fiber, glass fiber, aramidfiber, silicon carbide fiber, boron fiber, titanium alloy fiber, ultrahigh molecular weight polyethylene, or polybutylene terephthalate fiber;fiber reinforced resin including carbon fiber, glass fiber, aramidfiber, silicon carbide fiber, boron fiber, titanium alloy fiber, ultrahigh molecular weight polyethylene, or polybutylene terephthalate fiber;or nonmagnetic metal.
 10. A rotator comprising: a rotary shaft having anouter circumference surface expanding radially outward as extending in adirection from an axially first side toward an axially second side; andthe rotator member of claim 1, the rotator member being fixed to therotary shaft on a radially outside of the rotary shaft so that thesecond end of the sleeve is positioned at the axially second side of therotary shaft relative to the first end of the sleeve, wherein the sleeveis deformed so as to expand radially outward by the rotary shaft whenthe rotator member is fixed to the rotary shaft, so that the outercircumference surface of the sleeve and the inner circumference surfacesof the magnet segments are brought into a pressured contact with eachother.
 11. The rotator of claim 10, wherein the inner circumferencesurface of the sleeve and the outer circumference surface of the rotaryshaft contact each other in their almost entire areas where the tubularmember is disposed.
 12. The rotator of claim 10, wherein the sleevedeforms beyond its elastic deformation zone.
 13. A rotary electricmachine comprising the rotator of claim
 10. 14. The rotary electricmachine of claim 13, wherein the tubular member is given such aninterference that a fix torque between the sleeve and the rotary shaftexceeds the maximum torque of the rotary electric machine in an allowedrotation speed, and a fix torque between the magnet segments and thesleeve exceeds the maximum torque of the rotary electric machine in anallowed rotation speed.
 15. A method for manufacturing a rotator memberto be press fitted and fixed to a rotary shaft, the method comprising:disposing a plurality of magnet segments in the circumferentialdirection on an outer circumference surface of a tubular sleeve, thesleeve having a first end at an axially first side, a second end at anaxially second side, and an inner circumference surface including atapered surface that continuously expands radially outward as extendingin a direction from the first end toward the second end; and disposing atubular member to cover the plurality of magnet segments from a radiallyoutside.
 16. The method of claim 15, wherein the step of disposing thetubular member comprises directly winding a material of the tubularmember around the outer circumference of the magnet segments.
 17. Amethod for manufacturing a rotator for a rotary electric machineincluding the rotator member manufactured by the method of claim 15, themethod comprising: providing a rotary shaft, the rotary shaft having anouter circumference surface at an area where the rotator member isfixed, the outer circumference surface expanding radially outward asextending in a direction from an axially first side toward an axiallysecond side; and fixing the rotator member on a radially outside of therotary shaft by an interference fitting, wherein the step of fixing therotator member by the interference fitting comprising: fitting thesleeve over the rotary shaft from a side of the axially first side sothat the second end of the sleeve is positioned at the axially secondside of the rotary shaft relative to the first end; press fitting thesleeve over the rotary shaft so as to push the first end of the sleeveto the axially second side; and causing the sleeve to expand radiallyoutward by the force of press fitting the sleeve, while the sleeve ispress fitted to a predetermined fixing position.
 18. The method of claim17, wherein the rotator member includes a gap at least partially betweenthe sleeve and the magnet segments, wherein, in the step of fixing therotator member by the interference fitting, the outer circumferencesurface of the sleeve and the inner circumference surfaces of the magnetsegments are brought into contact in their almost entire areas bycausing the sleeve to expand radially outward so as to fill the gap. 19.The method of claim 18, wherein the outer circumference surface of thesleeve is cylindrical, wherein the inner circumference surface of eachmagnet segment is circularly arc and has a curvature radius that islarger than a radius of the outer circumference surface of the sleeve,wherein, in the step of fixing the rotator member by the interferencefitting, the outer circumference surface of the sleeve and the innercircumference surfaces of the magnet segments are brought into contactby causing the sleeve to expand radially outward.